Transmission of Power

Transmission of Electric Power: Plant to Home	Transformer: Theory of Operation

Transformer Equation From Faraday's law   Vsecondary = NsecondaryDFB/Dt            Vprimary = NprimaryDFB/Dt   Dividing the two, we arrive at the transformer equation   Vsecondary /Vprimary = NsecondaryDFB/Dt/NprimaryDFB/Dt   Vsecondary /Vprimary = Nsecondary/Nprimary     or     Vsecondary = Vprimary (Nsecondary/Nprimary )   To create a Step-up transformer: Nsecondary > Nprimary   To create a Step-down transformer: Nsecondary < Nprimary

Derivation of the Transformer Equations

Power Transmission: Plant to Home

Transformer Drum	Transmission Substation	Transmission Lines

Some of the many uses for transformers

ð Computer network interface cards

ð Modems

ð Power amlifiers

ð Microwave ovens

ð Car ignition systems

ð etc.

Why AC Used in Transmission of Power

The transformer equation does not work with DC - there is no changing magnetic field

Why Power Transmitted at High Voltages

Assume that 240 kW of electric power is consumed by a certain location that receives this power from 10 miles away over transmission lines.

The transmission lines have a total resistance of 0.40 ohms.

I = current in the lines = P/V

If the power is transmitted at 240 volts

I = 240,000 W/240 V = 1,000 A

P_loss = I²R = (1x10³  A)²(0.40 W) = 400,000 W loss if transmitted at 240 volts

If the power is transmitted at 24,000 volts

I = 240,000 W/24,000 V = 10 A

P_loss = I²R = (10  A)(0.40 W) = 4 W loss if transmitted at 24,000 volts